Quantitative description of configuration mixing in the interacting boson model

Shape coexistence inSe72investigated following theβdecay ofMcCutchan1, Lister2, Ahn3 et al. 2011Phys. Rev. C212230View full textAdd to dashboardCite

“…In these studies [21,22], it was found that the isotopes with N ≥ 40 could be well described, whereas significant discrepancies were found for the N < 40 isotopes, particularly in the energy of the 0 + 2 state. To incorporate the presence of shape coexistence, we performed IBM with configuration mixing [23,24] calculations (IBM-CM). Using the IBM-1 formalism where there is no distinction between protons and neutrons, the system is composed of regular states with the standard N bosons which mix with deformed states corresponding to N +2 bosons.…”

The Pt isotopes: Comparing the Interacting Boson Model with configuration mixing and the extended consistent-Q formalism

“…Figure 1 is characterized by a sudden drop of the first excited 0 + 2 state, down to mass A = 186, remaining essentially constant for lower mass numbers (down to mass A = 178). The energy spectrum remains remarkably constant in the mass interval 178 ≤ A ≤ 186, contrasting with a different structure that shows a number of up sloping levels with increasing mass number A beyond mass A = 186. excitations [29]. On the basis of intruder spin symmetry [33,73], no distinction is made between particle and hole bosons.…”

“…The truncation of the model space, however, by concentrating on nucleon pair modes (mainly 0 + and 2 + coupled pairs, to be treated as bosons within the Interacting Boson Approximation (IBM) [28]), has made the calculations feasible, even including pair excitations across the Z = 82 shell closure [29] in the Pb region. More in particular, the Pb nuclei have been extensively studied giving rise to bands with varying collectivity depending on the nature of the excitations treated in the model space [11,30,31,32,33,34,35,36,37].…”

“…Thus, it becomes clear that the Pt nuclei form a most important series of isotopes in order to study the above question. More specifically, within the IBM configuration-mixing approach [29] (IBM-CM for short), calculations have been carried out for the Pt nuclei by Harder et al [42] and by King et al [43] describing the low-lying excited states in the 168−196 Pt nuclei. In the latter studies, also g(2 + 1 ) factors and isotopic shifts were calculated and shown to be in good agreement with the known data [44,45].…”

Nuclear matrix elements for double-βdecay

“…Nonetheless, we will report, for the sake of completeness, also results for 48 Ca decay, with the proviso that these are rather approximate. Also, in some cases, intruder configurations play a role, especially in the structure of the excited 0 + state, and one needs to go to the configuration-mixing version IBM2-CM [31]. All these improvements will be reported in subsequent papers.…”